The overall objective of the proposed research is to determine the role of the viral genome in the production, expression and maintenance of-tumor transplantation antigen (TSTA) in cells transformed or infected with papovavirus SV40 and to investigate the relationship among TSTA and other surface changes. The induction of TSTA will be measured using in vitro techniques which specifically detect cellular immune reactivity. The role of the viral genome in the induction of TSTA will be investigated by using inhibitors and by isolating temperature-sensitive mutants of SV40 which are defective in the synthesis of TSTA at the nonpermissive temperature. This approach will allow us to determine which genes of SV40 are necessary for the production and maintenance of TSTA and whether the protein is coded for by the viral genome, as well as the role of TSTA in tumor rejection.